Electric brake system

ABSTRACT

An electric brake system that appropriately brakes a rotary body of a human powered vehicle in various situations is applicable to a human powered vehicle and includes a brake device including an electric actuator operated by electric power from a power supply, and a braking portion driven by the electric actuator to brake a rotary body of the human powered vehicle, a state detector detecting a state of the human powered vehicle other than an operation of the brake device performed by a user, and a control unit controlling the brake device so that the braking portion brakes the rotary body based on a detection result of the state detector.

BACKGROUND

An electric brake system including a brake device that includes anelectric actuator operated by electric power and a braking portiondriven by the electric actuator to brake a rotary body of a humanpowered vehicle is disclosed in Japanese Laid-Open Patent PublicationNo. 2017-30395 as an electric brake system applied to a human poweredvehicle.

SUMMARY

It is preferred that a brake be appropriately applied to a rotary bodyof a human powered vehicle in various situations.

An electric brake system according to a first aspect of one or moreexemplary embodiments is applicable to a human powered vehicle andincludes a brake device including an electric actuator operated byelectric power from a power supply, and a braking portion driven by theelectric actuator to brake a rotary body of the human powered vehicle, astate detector detecting a state of the human powered vehicle other thanan operation of the brake device performed by a user, and a control unitcontrolling the brake device so that the braking portion brakes therotary body based on a detection result of the state detector.

The brake device can be driven by an operation other than an operationintentionally performed by a user. Thus, it is possible to brake therotary body of the human powered vehicle appropriately in varioussituations.

In accordance with a second aspect of one or more exemplary embodiments,the electric brake system according to the first aspect is configured sothat the control unit controls the brake device to brake the rotary bodyrotating at a rotation speed that is higher than or equal to apredetermined rotation speed based on the detection result of the statedetector.

Thus, in a case where the rotation speed of the rotary body is lowerthan the predetermined speed, the user can move the human poweredvehicle. This ensures the convenience of the user.

In accordance with a third aspect of one or more exemplary embodiments,the electric brake system according to the first or second aspect isconfigured so that the control unit controls the brake device so that arotation speed of the rotary body is reduced in a stepped manner basedon the detection result of the state detector.

This prevents a quick reduction in the rotation speed of the rotarybody.

In accordance with a fourth aspect of one or more exemplary embodiments,the electric brake system according to any one of the first to thirdaspects is configured so that the braking portion includes a frictionmember pressed against the rotary body.

Thus, it is possible to easily brake the rotary body of the humanpowered vehicle.

In accordance with a fifth aspect of one or more exemplary embodiments,the electric brake system according to the fourth aspect is configuredso that the friction member includes a first friction member and asecond friction member arranged to face the first friction member withthe rotary body disposed between the first friction member and thesecond friction member, and the braking portion further includes a firstforward-reverse mechanism moving the first friction member forwardly andreversely with respect to the rotary body.

Thus, the first friction member is easily pressed against the rotarybody.

In accordance with a sixth aspect of one or more exemplary embodiments,the electric brake system according to the fifth aspect is configured sothat the braking portion further includes a second forward-reversemechanism moving the second friction member forwardly and reversely withrespect to the rotary body.

Thus, the second friction member is easily pressed against the rotarybody.

In accordance with a seventh aspect of one or more exemplaryembodiments, the electric brake system according to any one of the firstto sixth aspects is configured so that the state detector detects astate related to output of the power supply.

Thus, it is possible to brake the rotary body of the human poweredvehicle appropriately in accordance with the power supply state of thepower supply.

In accordance with an eighth aspect of one or more exemplaryembodiments, the electric brake system according to any one of the firstto seventh aspects further includes a power supply supplying electricpower to the electric actuator and a power storage provided separatelyfrom the power supply to supply electric power to the electric actuator.

According to this configuration, the electric actuator is driven usingelectric power of the power storage in accordance with the power supplystate of the power supply. Thus, it is possible to brake the rotary bodyof the human powered vehicle appropriately in various situations.

In accordance with a ninth aspect of one or more exemplary embodiments,the electric brake system according to the eighth aspect furtherincludes a charge controller controlling a charge state of the powerstorage so that the power storage maintains a state capable of supplyinga predetermined electric power to the electric actuator.

Thus, the brake device is maintained in a drivable state.

In accordance with a tenth aspect of one or more exemplary embodiments,the electric brake system according to the eighth or ninth aspect isconfigured so that the power supply includes a rechargeable battery.

Thus, the configuration of the power supply is simplified.

In accordance with an eleventh aspect of one or more exemplaryembodiments, the electric brake system according to the eighth or ninthaspect is configured so that the power supply includes an electric powergenerator generating electric power in accordance with traveling of thehuman powered vehicle.

According to this configuration, external electric power does not needto be supplied. Thus, the configuration of the power supply issimplified.

In accordance with a twelfth aspect of one or more exemplaryembodiments, the electric brake system according to any one of theeighth to eleventh aspects is configured so that the brake devicefurther includes a base provided with at least one of the electricactuator, the braking portion, and the power storage.

Thus, the configuration of the power supply is simplified. Additionally,electric power of the power storage is easily supplied to the electricactuator.

In accordance with a thirteenth aspect of one or more exemplaryembodiments, the electric brake system according to any one of the firstto seventh aspects further includes a power supply configured to supplyelectric power to the electric actuator and a further device other thanthe electric actuator.

According to this configuration, the control unit controls electricpower supplied from the power supply to the brake device and the furtherdevice based on the detection result of the state detector. Thus, it ispossible to brake the rotary body of the human powered vehicleappropriately in various situations.

In accordance with a fourteenth aspect of one or more exemplaryembodiments, the electric brake system according to the thirteenthaspect is configured so that the further device includes an assistdevice assisting propulsion of the human powered vehicle.

Thus, in a human powered vehicle including an assist device, it ispossible to brake the rotary body of the human powered vehicleappropriately in various situations.

In accordance with a fifteenth aspect of one or more exemplaryembodiments, the electric brake system according to any one of the firstto fourteenth aspects is configured so that the rotary body is a rotorprovided on a wheel of the human powered vehicle.

Thus, it is possible to effectively brake the wheel of the human poweredvehicle.

In accordance with a sixteenth aspect of one or more exemplaryembodiments, the electric brake system according to any one of the firstto fifteenth aspects is configured so that the brake device includes amaintenance mechanism maintaining a brake on the rotary body in a statewhere driving of the braking portion by the electric actuator isstopped.

Thus, the brake on the rotary body applied by the brake device is easilymaintained.

In accordance with a seventeenth aspect of one or more exemplaryembodiments, the electric brake system according to the sixteenth aspectis configured so that the maintenance mechanism is configured to bemanually set from a first state in which a braking force on the rotarybody is maintained by the braking portion to a second state in which thebraking force applied by the braking portion to the rotary body isreleased.

Thus, the maintenance mechanism is easily changed from the first stateto the second state.

In accordance with an eighteenth aspect of one or more exemplaryembodiments, the electric brake system according to the sixteenth orseventeenth aspect is configured so that the maintenance mechanism isconfigured to restrict driving of the braking portion caused by inputfrom the rotary body.

Thus, the configuration of the maintenance mechanism is simplified.

In accordance with a nineteenth aspect of one or more exemplaryembodiments, the electric brake system according to any one of the firstto eighteenth aspects further includes a notification device reporting abraking operation of the braking portion performed on the rotary bodybased on control of the control unit.

This allows the user to easily recognize that the brake is applied tothe rotary body.

With the electric brake system according to one or more of the exemplaryembodiments described herein, it is possible to brake a rotary body of ahuman powered vehicle appropriately in various situations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a vehicle to which a first embodiment of anelectric brake system is applied.

FIG. 2 is a block diagram showing the electric brake system of FIG. 1.

FIG. 3 is a diagram showing a maintenance mechanism of FIG. 2 in a firststate.

FIG. 4 is a diagram showing the maintenance mechanism of FIG. 2 in asecond state.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description related to each exemplary embodimentexemplifies, without any intention to limit, applicable forms of a brakedevice and an electric brake system. It will be apparent to the skilledartisan from this disclosure that the following descriptions ofexemplary embodiments are provided as examples only and need not limitthe broad inventive principles described herein or included in theappended claims. The brake device and the electric brake systemdescribed herein can be applicable to a form different from theexemplary embodiments such as modified examples of the exemplaryembodiments and combinations of at least two of the modified examplesthat do not contradict each other.

FIG. 1 shows a human powered vehicle A to which one exemplary embodimentof an electric brake system 10 is applied. The human powered vehicle Ais a city cycle that includes an assist device C assisting propulsion ofthe human powered vehicle A using electric energy. The configuration ofthe human powered vehicle A can be changed to any configuration. Thehuman powered vehicle A can be configured without the assist device C.The type of the human powered vehicle A can be a road bike, a mountainbike, or a cross bike. As shown in FIG. 1, the human powered vehicle Aincludes a body A1, a handlebar A2, a wheel A3 (front wheel A3), a wheelA4 (rear wheel A4), a drive mechanism B, the assist device C, anoperating device D, an external shifting device E, and the electricbrake system 10. The human powered vehicle A further includes a torquesensor and a vehicle speed sensor (not shown). The body A1 includes aframe A12.

The drive mechanism B transmits human power to the rear wheel A4. Thedrive mechanism B is configured to be a chain drive type and includes afront sprocket B1, a rear sprocket B2, a chain B3, a crank mechanism G,and a pair of pedals B4. The drive mechanism B can be selected from anytype and can be a belt drive type or a shaft drive type.

The crank mechanism G includes a crankshaft G1, a right crank G2, and aleft crank G3. The crankshaft G1 is rotatably supported by a bottombracket provided on the frame A12. The right crank G2 and the left crankG3 are coupled to the crankshaft G1. One of the pair of pedals B4 isrotatably supported by the right crank G2. The other (not shown) of thepair of pedals B4 is rotatably supported by the left crank G3.

The front sprocket B1 is coupled to the crankshaft G1. The crankshaft G1and the front sprocket B1 are coaxial. Any structure related to thecoupling of the crankshaft G1 and the front sprocket B1 can be selected.A one-way clutch (not shown) is provided between the crankshaft G1 andthe front sprocket B1. The one-way clutch transmits rotation of thecrankshaft G1 to the front sprocket B1 in a case where the crankshaft G1is rotating forward at a rotation speed that is higher than a rotationspeed of the front sprocket B1. The front sprocket B1 and the crankshaftG1 can be coupled so as not to rotate relative to each other asnecessary.

The rear sprocket B2 is rotatably supported by the rear wheel A4. Thechain B3 runs around the front sprocket B1 and the rear sprocket B2. Ina case where the crankshaft G1 and the front sprocket B1 are rotatedforward by human power applied to the pair of pedals B4, the rear wheelA4 is rotated forward by the human power transmitted via the chain B3and the rear sprocket B2.

The assist device C includes an assist motor C1, a drive circuit C2, aspeed reduction unit C3, and a one-way clutch (not shown). The assistdevice C assists propulsion of the human powered vehicle A bytransmitting torque to the front sprocket B1. The torque sensor outputsa signal corresponding to torque applied to a detection subject. Thedetection subject of the torque sensor is, for example, the crankshaftG1 or the pedals B4. In a case where the detection subject is thecrankshaft G1 or the pedals B4, the torque sensor outputs a signalcorresponding to human power applied to the crankshaft G1 or the pedalsB4. Any specific configuration of the torque sensor can be selected. Thetorque sensor includes a strain sensor, a magnetostriction sensor, anoptical sensor, or a pressure sensor.

The operating device D includes an operating portion D1 and an operatingportion D2 operated by the user. The operating portion D1 is one ormultiple buttons. The operating portion D2 is an operating lever. Theoperating device D is connected to communicate with the externalshifting device E, the assist device C, and the electric brake system 10so that a signal corresponding to an operation of at least one of theoperating portion D1 and the operating portion D2 is transmitted to theexternal shifting device E, the assist device C, and the electric brakesystem 10. The operating device D is connected to communicate with theexternal shifting device E, the assist device C, and the electric brakesystem 10 by a wire configured to perform power line communication (PLC)or a communication line. Alternatively, the operating device D can beconnected to communicate with the external shifting device E, the assistdevice C, and the electric brake system 10 by a wireless communicationunit configured to perform wireless communication. In a case where theoperating portion D1 is operated, a signal for changing an assist modeof the assist device C is transmitted to the assist device C, and theassist mode of the assist mechanism is changed in accordance with thesignal. In a case where the operating portion D2 is operated, a signalfor braking at least one of the front wheel A3 and the rear wheel A4 istransmitted to a control unit 14 (refer to FIG. 2) of the electric brakesystem 10, and a brake device 12 is operated in accordance with thesignal.

As shown in FIG. 2, the electric brake system 10 includes the brakedevice 12, the control unit 14, and a state detector 18. Preferably, theelectric brake system 10 includes a power supply 16 and a notificationdevice 22.

The brake device 12 is applicable to the human powered vehicle A. Anytype of the brake device 12 can be selected. In the present embodiment,the brake device 12 is a disc brake device that brakes rotary body H(refer to FIG. 1) of the human powered vehicle A, and the rotary body His a rotor provided on each of the front wheel A3 and the rear wheel A4of the human powered vehicle A. The brake device 12 can be a rim brakedevice that brakes a rim I (refer to FIG. 1) of each of the front wheelA3 and the rear wheel A4 of the human powered vehicle A. The brakedevice 12 shown in FIG. 2 includes an electric actuator 24, a brakingportion 26, and a power storage 28. Preferably, the brake device 12includes a base 30 and a maintenance mechanism 32.

The electric actuator 24 is operated by electric power from the powersupply 16. In the present embodiment, the electric actuator 24 is anelectric motor. The electric actuator 24 is connected to the brakingportion 26. The braking portion 26 is driven by the electric actuator 24to brake the rotary body H (refer to FIG. 1) of the human poweredvehicle A.

As shown in FIG. 3, the braking portion 26 includes a friction member34, a first forward-reverse mechanism 36, a second forward-reversemechanism 38, and a force transmission mechanism 40. The friction member34 is pressed against the rotary body H by the forward-reversemechanisms 36 and 38. Thus, the brake is easily applied to the rotarybody H of the human powered vehicle A. In the present embodiment, thefriction member 34 includes disc brake pads. The friction member 34includes a first friction member 34A and a second friction member 34B.The first friction member 34A is arranged to face one surface HA of therotary body H. The first friction member 34A brakes the rotary body H bybeing pressed against the one surface HA of the rotary body H by thefirst forward-reverse mechanism 36. The second friction member 34B isarranged to face the other surface HB of the rotary body H.Additionally, the second friction member 34B is arranged to face thefirst friction member 34A with the rotary body H disposed therebetween.The second friction member 34B brakes the rotary body H by being pressedagainst the other surface HB of the rotary body H by the secondforward-reverse mechanism 38.

The first forward-reverse mechanism 36 moves the first friction member34A forwardly and reversely with respect to the rotary body H. (Here,forward and reverse refer to a direction along an axis of the rotarybody H and do not correspond to the travel direction of the humanpowered vehicle A.) Thus, the first friction member 34A is easilypressed against the rotary body H. The second forward-reverse mechanism38 moves the second friction member 34B forwardly and reversely withrespect to the rotary body H. Thus, the second friction member 34B iseasily pressed against the rotary body H. In the present embodiment, thefirst forward-reverse mechanism 36 and the second forward-reversemechanism 38 are rotatably provided on the base 30 (housing). The firstforward-reverse mechanism 36 is biased by a biasing member (not shown)in a direction in which the first friction member 34A separates awayfrom the rotary body H. The second forward-reverse mechanism 38 isbiased by a biasing member (not shown) in a direction in which thesecond friction member 34B separates away from the rotary body H.

The force transmission mechanism 40 couples the electric actuator 24 tothe first forward-reverse mechanism 36 and the second forward-reversemechanism 38. The force transmission mechanism 40 includes a bolt 42, amoving member 44, and guide members 45A and 45B. The bolt 42 is coupledto an output shaft 24A of the electric actuator 24 via the maintenancemechanism 32. The bolt 42 is inserted into the moving member 44.Rotation of the moving member 44 in accordance with rotation of the bolt42 is restricted by the guide members 45A and 45B. The moving member 44is guided by the guide members 45A and 45B to move in an axial directionof the bolt 42 in accordance with rotation of the bolt 42. Morespecifically, the force transmission mechanism 40 is configured to be aball screw that converts rotational motion of the electric actuator 24,which is an electric motor, into linear motion of the moving member 44.

The moving member 44 is arranged to push the first forward-reversemechanism 36 and the second forward-reverse mechanism 38. An end portion44A of the moving member 44 is wedge-shaped. The first forward-reversemechanism 36 includes a contact portion 36A having a shape correspondingto the end portion 44A. The second forward-reverse mechanism 38 includesa contact portion 38A having a shape corresponding to the end portion44A. Rotation of the bolt 42 in a first direction moves the movingmember 44 toward the first forward-reverse mechanism 36 and the secondforward-reverse mechanism 38 in the axial direction of the bolt 42. Theend portion 44A of the moving member 44 contacts the contact portions36A and 38A to pivot the first forward-reverse mechanism 36 and thesecond forward-reverse mechanism 38 against the biasing force of thebiasing members. As a result, as shown in FIG. 3, the first frictionmember 34A and the second friction member 34B are pressed against therotary body H, braking the rotary body H. Rotation of the bolt 42 in asecond direction that is opposite to the first direction moves themoving member 44 away from the first forward-reverse mechanism 36 andthe second forward-reverse mechanism 38 in the axial direction of thebolt 42. As a result, as shown in FIG. 4, the biasing force of thebiasing members pivots the first forward-reverse mechanism 36 and thesecond forward-reverse mechanism 38 so that the first friction member34A and the second friction member 34B separate from the rotary body H.

The power storage 28 shown in FIG. 2 is provided separately from thepower supply 16 to supply electric power to the electric actuator 24.The power storage 28 includes a storage battery or a capacitor. Thestorage battery is a lead storage battery, a nickel-metal hydridebattery, or a lithium-ion battery. The power storage 28 is connected tothe control unit 14 and the power supply 16. The power storage 28 storeselectric power supplied from, for example, the power supply 16.

The base 30 is provided with the electric actuator 24, the brakingportion 26, and the power storage 28. The base 30 is a case configuredto accommodate the control unit 14, the power supply 16, the electricactuator 24, the power storage 28, and the state detector 18. Thus, thepower supply 16, the electric actuator 24, the power storage 28, and thestate detector 18 are protected.

The power supply 16 supplies electric power to the electric actuator 24and the power storage 28. Any configuration of the power supply 16 canbe selected. For example, the power supply 16 includes a rechargeablebattery. In a case where the power supply 16 is a rechargeable battery,as shown in FIG. 1 by the single-dashed lines, the power supply 16 isarranged on any position of the body A1. Additionally, for example, thepower supply 16 includes an electric power generator that generateselectric power in accordance with traveling of the human powered vehicleA. One example of the electric power generator is a dynamo. In a casewhere the power supply 16 is an electric power generator (dynamo), thepower supply 16 is, for example, a hub dynamo provided on the frontwheel A3.

The state detector 18 detects a state of the human powered vehicle Aother than an operation of the brake device 12 performed by the user.The state detector 18 detects a state related to output of the powersupply 16 (hereafter, referred to as “output state”). Any specificcontent of the output state detected by the state detector 18 can beselected. In the present embodiment, the state detector 18 detects thevoltage of the power supply 16. In a case where the state detector 18detects an abnormality of the power supply 16 based on variations in thevoltage of the power supply 16, the state detector 18 sends an abnormalsignal to a drive controller 46 of the control unit 14. The statedetector 18 can be configured to detect a charge-discharge amount of thepower supply 16. In this case, if the state detector 18 detects anabnormality of the power supply 16 based on the charge-discharge amountof the power supply 16, the state detector 18 sends an abnormal signalto the drive controller 46 of the control unit 14. With no limit to thedetection of the output state, any device that detects a state of thehuman powered vehicle A other than the operation of the brake device 12can be used as the state detector. For example, a device that detects acommunication state of an electrical component or a device that detectsa travel state of the human powered vehicle A such as speed,acceleration, cadence, or inclination can be used as the state detector.

In the present embodiment, the control unit 14 is a central processingunit (CPU) or a micro processing unit (MPU). The CPU or MPU configuredto be the control unit 14 also functions as the drive controller 46 anda charge controller 48. Any specific configuration of the control unit14, the drive controller 46, and the charge controller 48 can beselected. For example, separate CPUs or MPUs can be prepared as each ofthe control unit 14, the drive controller 46, and the charge controller48. Alternatively, two CPUs or MPUs can be prepared, and the functionsof the control unit 14, the drive controller 46, and the chargecontroller 48 can be divided between the two CPUs or MPUs. The mountlocation of a CPU or MPU configured to be the control unit 14, the drivecontroller 46, and the charge controller 48 is not limited to the base30 and can be any location.

The drive controller 46 performs normal control and emergency control.Normal control is performed based on a signal from the operating portionD2 (refer to FIG. 1) of the operating device D. In normal control, thedrive controller 46 drives the electric actuator 24 by electric power ofat least one of the power supply 16 and the power storage 28. In normalcontrol, the drive controller 46 operates the electric actuator 24 byelectric power of the power supply 16 and electric power of the powerstorage 28 based on the detection result of the state detector 18. Inthis manner, the electric power of the power supply 16 and the electricpower of the power storage 28 are overlapped as necessary. Thus, theelectric actuator 24 is stably operated. Emergency control is performedbased on an input of the abnormal signal from the state detector 18. Inemergency control, even in a case where there is no input of a signalfrom the operating portion D2, the drive controller 46 controls thebrake device 12 so that the braking portion 26 brakes the rotary body H(refer to FIG. 1). In emergency control, the drive controller 46controls the brake device 12 so as to brake the rotary body H that isrotating at a rotation speed higher than or equal to a predeterminedrotation speed. Thus, in a case where the rotation speed of the rotarybody H is lower than the predetermined speed, the user can move thehuman powered vehicle A. This ensures the convenience of the user. Thepredetermined rotation speed is set to be higher than a normal speed atwhich the user is assumed to walk the human powered vehicle A. In oneexample, the predetermined rotation speed is set to the rotation speedin a case where the user is walking the human powered vehicle A at 7 kmper hour. Additionally, in emergency control, the drive controller 46controls the brake device 12 so that the rotation speed of the rotarybody H is reduced in a stepped manner. This limits a quick reduction ofthe rotation speed of the rotary body H. In emergency control, the drivecontroller 46 operates the electric actuator 24 by only electric powerof the power storage 28. Thus, even in a case where the electricactuator 24 is not supplied with sufficient electric power from thepower supply 16, the brake device 12 is drivable.

The charge controller 48 controls the charge state of the power storage28 so that the power storage 28 maintains a state capable of supplying apredetermined electric power to the electric actuator 24. Thepredetermined electric power is electric power that is large enough forthe braking portion 26 to brake rotary body H (refer to FIG. 1) and stopthe rotary body H at least one time in a case where the drive controller46 performs emergency control to drive the brake device 12. Preferably,the predetermined electric power is large enough for the braking portion26 to brake the rotary body H and stop the rotary body H multiple times.

In a case where emergency control is performed in a state where thedriving of the braking portion 26 by the electric actuator 24 isstopped, the maintenance mechanism 32 maintains the brake on the rotarybody H. The maintenance mechanism 32 is configured to restrict thedriving of the braking portion 26 caused by input from the rotary bodyH. Thus, the configuration of the maintenance mechanism 32 issimplified. As shown in FIG. 3, the maintenance mechanism 32 is arrangedbetween the output shaft 24A of the electric actuator 24 and the bolt 42of the force transmission mechanism 40. The maintenance mechanism 32allows transmission of rotational force to the bolt 42 from a side ofthe electric actuator 24 (upstream side) with respect to the maintenancemechanism 32. The maintenance mechanism 32 restricts transmission ofrotational force to the bolt 42 from a side of the bolt 42 (downstreamside) with respect to the maintenance mechanism 32. The maintenancemechanism 32 is configured to be manually set from a first state (referto FIG. 3) in which the brake on the rotary body H is maintained by thebraking portion 26 to a second state (refer to FIG. 4) in which thebrake applied by the braking portion 26 to the rotary body H isreleased. The output shaft 24A of the electric actuator 24 is providedwith a user operating portion 24B. In the first state shown in FIG. 3,the user rotates the user operating portion 24B of the output shaft 24Aso that the bolt 42 is rotated in the second direction to change themaintenance mechanism 32 to the second state shown in FIG. 4. Thus, theuser can easily change the maintenance mechanism 32 from the first stateto the second state.

The notification device 22 shown in FIG. 2 reports the braking operationof the braking portion 26 performed on the rotary body H based onemergency control of the drive controller 46. In a case where the drivecontroller 46 performs emergency control, the notification device 22notifies the user that emergency control is performed based on at leastone of sound, light, and vibration. The notification device 22 isarranged, for example, on the handlebar A2 (refer to FIG. 1) togetherwith the operating device D.

The electric brake system 10 and the brake device 12 have the effect andadvantages descried below. The electric actuator 24 is driven usingelectric power of the power storage 28 in accordance with the powersupply state from the power supply 16. Thus, it is possible to brake therotary body H of the human powered vehicle A appropriately in varioussituations.

Another operation of the electric brake system 10 will now be described.The drive controller 46 of the electric brake system 10 controls drivestates of the brake device 12 and a further device based on thedetection result of the state detector 18. The drive controller 46decreases the supply of electric power to the further device based on adetection of a decrease in the output of the power supply 16 by thestate detector 18. Thus, the brake device 12 is maintained in a drivablestate. The drive controller 46 stops the supply of electric power to thefurther device based on a state in which the state detector 18 detectsthat the output of the power supply 16 is lower than a threshold value.Thus, the brake device 12 is further assuredly maintained in a drivablestate. In a case where the state detector 18 detects that the output ofthe power supply 16 is lower than the threshold value, the statedetector 18 sends an abnormal signal to the drive controller 46. Thedrive controller 46 performs emergency control based on the input of theabnormal signal.

The electric brake system 10 has the effect and advantages describedbelow. The drive controller 46 controls the supply of electric powerfrom the power supply 16 to the brake device 12 and the further devicebased on the detection result of the state detector 18. Thus, it ispossible to brake the rotary body H of the human powered vehicle Aappropriately in various situations.

The invention claimed is:
 1. An electric brake system applicable to ahuman powered vehicle, the electric brake system comprising: a brakedevice including: an electric actuator operated by electric power from apower supply; and a braking portion driven by the electric actuator tobrake a rotary body of the human powered vehicle; an emergency statedetector detecting an emergency state of the human powered vehicle otherthan an operation of the brake device performed by a user; and a controlunit controlling the brake device so that (i) a rotation speed of therotary body is reduced in a stepped manner based on the detection of theemergency by the emergency state detector, and (ii) the reduction of thespeed of the rotary body stops at a first predetermined rotation speedthat is equivalent to a walking speed of a human.
 2. The electric brakesystem according to claim 1, wherein the control unit controls the brakedevice to brake the rotary body rotating at a rotation speed that ishigher than or equal to a second predetermined rotation speed based onthe detection result of the emergency state detector.
 3. The electricbrake system according to claim 1, wherein the braking portion includesa friction member pressed against the rotary body.
 4. The electric brakesystem according to claim 3, wherein the friction member includes afirst friction member and a second friction member arranged to face thefirst friction member with the rotary body disposed between the firstfriction member and the second friction member, and the braking portionfurther includes a first forward-reverse mechanism moving the firstfriction member forwardly and reversely with respect to the rotary body.5. The electric brake system according to claim 4, wherein the brakingportion further includes a second forward-reverse mechanism moving thesecond friction member forwardly and reversely with respect to therotary body.
 6. The electric brake system according to claim 1, whereinthe emergency state detector detects a state related to output of thepower supply.
 7. The electric brake system according to claim 1, furthercomprising: a power storage provided separately from the power supply tosupply electric power to the electric actuator.
 8. The electric brakesystem according to claim 7, further comprising a charge controllercontrolling a charge state of the power storage so that the powerstorage maintains a state capable of supplying a predetermined electricpower to the electric actuator.
 9. The electric brake system accordingto claim 7, wherein the power supply includes a rechargeable battery.10. The electric brake system according to claim 7, wherein the powersupply includes an electric power generator generating electric power inaccordance with traveling of the human powered vehicle.
 11. The electricbrake system according to claim 7, wherein the brake device furtherincludes a base provided with at least one of the electric actuator, thebraking portion, and the power storage.
 12. The electric brake systemaccording to claim 1, wherein the power supply is configured to supplyelectric power to the electric actuator and a further device other thanthe electric actuator.
 13. The electric brake system according to claim12, wherein the further device includes an assist device assistingpropulsion of the human powered vehicle.
 14. The electric brake systemaccording to claim 1, wherein the rotary body is a rotor provided on awheel of the human powered vehicle.
 15. The electric brake systemaccording to claim 1, wherein the brake device includes a maintenancemechanism maintaining a brake on the rotary body in a state wheredriving of the braking portion by the electric actuator is stopped. 16.The electric brake system according to claim 15, wherein the maintenancemechanism is configured to be manually set from a first state in which abraking force on the rotary body is maintained by the braking portion toa second state in which the braking force applied by the braking portionto the rotary body is released.
 17. The electric brake system accordingto claim 15, wherein the maintenance mechanism is configured to restrictdriving of the braking portion caused by input from the rotary body. 18.The electric brake system according to claim 1, further comprising anotification device reporting a braking operation of the braking portionperformed on the rotary body based on control of the control unit. 19.The electric brake system according to claim 1, wherein the walkingspeed of a human is about 7 km per hour.